const redux = require('redux')

const initialState = {
  counter: 0
}

// reducer
function reducer(state = initialState, action) {
  switch (action.type) {
    case "INCREMENT":
      return { ...state, counter: state.counter + 1 }
    case "DECREMENT":
      return { ...state, counter: state.counter - 1 }
    case "ADD_NUMBER":
      return { ...state, counter: state.counter + action.num }
    case "SUB_NUMBER":
      return { ...state, counter: state.counter - action.num }
    default:
      return state
  }
}

// store(创建时需要传入一个reducer)
const store = redux.createStore(reducer)

// 订阅store的修改
store.subscribe(()=>{
  console.log("counter:",store.getState());
})

// actions
const action1 = { type: "INCREMENT" }
const action2 = { type: "DECREMENT" }

const action3 = { type: "ADD_NUMBER", num: 5 }
const action4 = { type: "SUB_NUMBER", num: 12 }

// 派发action
store.dispatch(action1)
store.dispatch(action2)
store.dispatch(action2)
store.dispatch(action3)
store.dispatch(action4)



